[1] Univ N Carolina, Dept Epidemiol, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Dept Med, Chapel Hill, NC 27599 USA
[3] Kilimanjaro Christian Med Ctr, Moshi, Tanzania
[4] Campbell Univ, Dept Biol, Buies Creek, NC 27506 USA
[5] Abbott Labs, Expt Biol Res, N Chicago, IL 60064 USA
[6] Duke Univ, Med Ctr, Div Infect Dis & Int Hlth, Durham, NC USA